Project Summary The long-term goal of our research is to understand the molecular mechanisms that control centriole biogenesis and how errors in this process contribute to human disease. Centrioles are the structural core of centrosomes, organelles that nucleate microtubules to build mitotic/meiotic spindles and cilia. During a normal cell cycle, centrioles duplicate once to ensure their copy number is precisely maintained. The presence of supernumerary centrioles is a common feature of human tumors and can promote chromosome segregation errors that are sufficient to drive tumor development in mice. To maintain genome integrity, cells have evolved a protective centriole surveillance pathway to restrict the proliferation of cells with extra centrioles. The goal of our application is to unravel the molecular mechanism responsible for ?sensing? supernumerary centrioles and evaluate whether inactivation of this pathway facilitates tumor development in cells with extra centrioles. Centriole amplification triggers the activation of the PIDDosome, a trimeric protein complex that acts as an activation platform for Caspase-2. Once activated, Caspase-2 promotes the cleavage of MDM2 and subsequent stabilization of P53. However, there exists a gap in our understanding of how extra centrioles are sensed and how this information is relayed to the PIDDosome to trigger P53 activation. To address this knowledge gap, we developed a genome-wide screening approach to identify genes required to arrest the growth of non-transformed cells with extra centrioles. Our preliminary data show that distal appendages that form on mature centrioles are responsible for activating the PIDDosome following centriole amplification. In Aim 1 of this proposal we will use cell biological, genetic and biochemical approaches to mechanistically dissect how cells ?sense? supernumerary centrioles to trigger PIDDosome activation. In Aim 2, we will determine the impact of specifically inactivating the centriole surveillance pathway on the proliferation and oncogenic transformation of cells with extra centrioles in vivo. We are well suited to pursue these studies given our expertise in studying centriole biology; our development of a unique mouse model to study the impact of centriole amplification in vivo; and our collaborative relationship with the Regot and Loncarek laboratories, who are world-experts in high resolution live-cell imaging and correlative light/EM analysis of centriole ultrastructure. Understanding how normal cells detect centriole amplification addresses a fundamental question that will provide insight into how aneuploid tumor cells adapt to proliferate robustly with extra centrioles.